StarDate Podcast

A half a century ago, the swan’s tail feathers got a little singed. A bright “new” star – a nova – flared into view close to Deneb, the star that represents the tail. Known today as V1500 Cygni, it was one of the brightest novas ever seen. In a matter of hours, it grew about 40 million times brighter. It was visible to the unaided eye for several nights. And it took months to fade to its previous brightness. V1500 is actually two stars. One of them is a heavy white dwarf – a hot, dense “corpse.” The other is a red dwarf – a small, cool, faint star that’s still in the prime of life. The white dwarf is pulling gas from its feeble companion. Powerful magnetic fields funnel it onto the white dwarf. As the gas piles up on the white dwarf, the dead star’s gravity squeezes it into a thin layer, making the gas hotter and hotter. In 1975, that layer got so hot that it exploded in a massive nuclear inferno. The blast disrupted the flow of material, and heated the surface of its companion – which is still cooling off. Today, the white dwarf is stealing more gas from the companion. So it may flare up again in the centuries ahead – making things a bit uncomfortable for the tail of the swan. Cygnus is high in the east at nightfall, anchored by Deneb. V1500 is close to the lower left of Deneb, but much too faint to see without a telescope – for now. Script by Damond Benningfield

Corona Borealis, the northern crown, could be about to add another jewel – at least for a while. A star system there has been flaring up every 80 years. The last outburst was in 1946, so it’s due for the next one. T Corona Borealis is actually a binary – two stars locked in a mutual orbit. One of them is a white dwarf – the “corpse” of a star that was once like the Sun. The other is a red giant – a star that’s puffed up as it nears the end of its own life. The white dwarf pulls hydrogen off the surface of its bloated companion. The gas forms a spinning disk around the white dwarf. Gas at the inner edge of the disk spirals onto the white dwarf. The white dwarf’s gravity is quite strong, so the infalling gas is squeezed into a thin layer and heated to tens of millions of degrees. That eventually triggers a runaway nuclear explosion – like a giant hydrogen bomb. The outburst is known as a nova – a Latin word that means “new.” When the “bomb” goes off, the system shines tens of thousands of times brighter than average. That makes it visible to the eye alone, even though it’s 3,000 light-years away. So keep an eye out for this “new” jewel in the northern crown. Corona Borealis is high in the southwest at nightfall. It’s an upside-down semicircle of stars, with the brightest star at its middle. T Corona is close to the top left end of the semicircle. We’ll talk about another bright nova tomorrow. Script by Damond Benningfield

There are no traffic signals in lunar orbit. And for the most part, they’re not needed – at least not yet. Only about a dozen spacecraft are circling the Moon. But every once in a while, they can pass dangerously close to each other. And that triggers a “red alert” – a warning to the operators of both craft. It might sound surprising that there’s ever any kind of problem – there’s a lot of space around the Moon. But many of the spacecraft follow similar orbits. Many of them orbit from pole to pole, allowing them to study the entire lunar surface. And there’s no system for tracking the second-by-second locations of the orbiters. Instead, NASA engineers with a project called MADCAP track the “orbital elements” of every craft in orbit around the Moon and Mars – a set of details that includes altitude, the angle of the orbit, and much more. Computers constantly plot the motions of every craft for which they have those details. If it looks like there might be a dangerously close encounter, the alert goes out. Operators of the conflicting missions then get together to find a solution. Overall, the number of alerts is small. But in December 2024 it jumped to more than 20. And with more lunar missions scheduled, we can expect more “red alerts” in the years ahead. The crescent Moon is in the west as darkness falls. The brilliant planet Venus – the “evening star” – is close to the right. Script by Damond Benningfield

Stars age in a well-understood way. Nuclear fusion in a star’s core converts lighter elements to heavier ones. At some point, that process ends and the star dies. How long the star lives and how it does so are determined by its mass. But a recent study says that some stars could be powered in part by dark matter. That could affect how long the stars live, and make them look younger than they really are. Dark matter accounts for about 85 percent of all the matter in the universe. It produces no energy. We know it’s there only because its gravity tugs the visible matter around it. It may consist of some type of subatomic particle, but no one’s found it. But if certain types of dark-matter particles ram together, they may cancel each other with a flash. The study says that could impact stars in the center of the galaxy, where dark matter is tightly packed. Massive stars, with stronger gravity, could pull in more dark matter. That would keep them going practically forever. And it would make them look younger. Lighter stars couldn’t pull in enough dark matter to keep them going. Instead, the dark-matter reactions would blow the stars apart. A cluster at the heart of the galaxy contains many heavy stars that look young in some ways, but old in others. And the cluster doesn’t have any lightweight stars. That combination could mean that the evolution of the stars in that region is being influenced by dark matter. Script by Damond Benningfield

Something small, dark, and heavy lurks at the heart of the Milky Way Galaxy. Most astronomers say it’s a black hole. But a recent study says “not so fast”- it could be a clump of dark matter. The central object is called Sagittarius A-star. It’s about 4.3 million times the mass of the Sun. A few years ago, astronomers took a picture of its “shadow” against a glowing background. Sagittarius A-star is encircled by stars and dusty clumps in tight orbits. They’re accelerated to millions of miles per hour by the gravity of the central object. The new study suggested that object could be a knot of dark matter particles known as fermions. Dark matter produces no detectable energy, but its gravity pulls on the visible matter around it. It appears to make up about 85 percent of all the matter in the universe, but its nature remains unknown. The clump could account for many of the observed qualities of the central dark object. Other studies have suggested that dark matter could produce fountains of gamma rays that shoot from the galaxy’s core. Dark-matter particles could produce the gamma rays when they ram together and cancel each other out. The dark-matter model doesn’t explain all of the evidence of a black hole. But future instruments should be able to discern between the two models – providing a definitive explanation for the darkness at the galaxy’s heart. More about dark matter tomorrow. Script by Damond Benningfield

Our solar system is passing through one of the spiral arms that makes the Milky Way Galaxy look like a pinwheel. But the key words there are “passing through.” The solar system moves through the galaxy a little faster than the spiral arms do. So over hundreds of millions of years, we cross all of the galaxy’s major arms. And those crossings could be dangerous. A spiral arm is a region where a passing wave squeezes giant clouds of gas and dust, triggering the birth of new stars. Many of the stars are especially hot and bright, so they light up the spiral arms. The star-forming clouds are dense and turbulent. And a recent study suggested that could be where the “danger” comes in. Researchers looked at tiny crystals in Earth’s crust. They found that the composition of the crystals varied over periods of hundreds of millions of years. During some of those periods, Earth’s crust appeared to be especially hot. And the timing of those periods may correspond to passages through the spiral arms. As we move through the dense clouds in the arms, big balls of ice and rock far from the Sun could be nudged inward. Some of them could ram into Earth, creating conditions that could account for some of the crystals. So while the Milky Way’s spiral arms may be beautiful, they may also be deadly. Look for the glowing band of the Milky Way curving across the east as night falls, and arching high overhead later on. Script by Damond Benningfield

The Milky Way shines at its best on summer nights. Right now, it arcs across the east as the sky gets fully dark, and passes high overhead later on. Under dark skies, it looks like a hazy band of light. That band outlines the disk of our home galaxy. So for the astronomers who study the Milky Way Galaxy, it’s the go-zone – there’s lots to look at. But for those who study other galaxies, it’s been the no-go zone. In fact, it’s called the Zone of Avoidance, because it’s hard to see anything through it. The main problem is giant clouds of dust scattered throughout the galaxy. The dust absorbs visible light. Depending on which part of the disk you look through, in fact, the clouds can block more than 99 percent of the light from objects behind them. The other problem is that the Milky Way is crowded – millions upon millions of stars everywhere you look. So when you look into the band of the Milky Way, it’s hard to know whether you’re seeing a star or gas cloud in the galaxy or something beyond it. Fortunately, some wavelengths that are invisible to the human eye do get through: infrared light and radio waves. The infrared is best seen from space, but the radio can be turned in by giant antennas on the ground. Galaxies typically emit more of both of those forms of energy than individual stars do – important ways to avoid problems from the Zone of Avoidance. More about the Milky Way tomorrow. Script by Damond Benningfield

It’s hard to map a forest when you’re standing in the middle of it. You see the trees that are close by, but most of the forest is blocked out. Astronomers have faced the same challenge when trying to map the Milky Way Galaxy. We’re right in the middle of it, surrounded by bright stars and dark dust clouds. So we can’t get an overall picture of the whole thing. But nature has provided a way to see the forest through the trees: galactic radio. Big clouds of hydrogen gas emit radio waves at a wavelength of 21 centimeters – eight and a quarter inches. The radio waves pass through the intervening material, giving us a good outline of the structure of the Milky Way. That wavelength is produced when hydrogen atoms get “bumped up” to a higher energy level. When the atoms drop back to their base level, they emit radio waves. This process plays out most commonly in clouds where new stars are being born. Mapping the clouds revealed that the Milky Way is a spiral galaxy – a beautiful cosmic pinwheel. And measuring the motions of the clouds reveals how that pinwheel spins. So a lot of what we know about the Milky Way has come to us through the broadcasts of “galactic radio.” The Milky Way arcs across the east as night falls. You need dark skies to see it. The center of the galaxy is in Sagittarius, which is low in the southeast. It’s easy to pick out because its stars form the outline of a teapot. Script by Damond Benningfield

The center of the Milky Way Galaxy is in good view as night falls this evening. And as the night ends, at dawn tomorrow, the galactic “anticenter” is in view – the point directly opposite the center. The Milky Way is our home galaxy. It’s a disk about a hundred-thousand light-years wide. Earth is about half-way between the center of the disk and its rim. In the night sky, the disk forms the faint path called the Milky Way. But you need nice dark skies to see it. The center is in the constellation Sagittarius. Its most prominent stars form the outline of a teapot. Puffs of “steam” appear to rise from the spout of the teapot. The center of the galaxy is immersed in the steam. We can’t see the center because intervening clouds of dust absorb its light. But if we could see it, it would be impressive. Billions of stars are jammed together – far more tightly packed than in our region of the galaxy. The anti-center is in Taurus, which is low in the east at dawn. That point is marked by the star Elnath. It’s the bull’s second-brightest star, at the tip of one of his horns. And it’s easy to spot tomorrow because it’s quite close to the crescent Moon. Except for Elnath, there’s not much to see in that direction. We’re looking toward the galaxy’s thinly settled outer precincts, with intergalactic space beyond. Enjoy the panorama of the Milky Way – our galactic home – all night long. Script by Damond Benningfield

Future spelunkers might want to explore caves on the Moon and Mars. Scientists have mapped many cave openings on both worlds. On the Moon, caves could provide shelter from radiation and meteorites for astronauts. On Mars, they could provide shelter for microscopic life that was born on the planet itself. Orbiting spacecraft have photographed some likely cave entrances on both worlds. They’re big holes in the ground. They may lead to larger chambers on the sides. On the Moon, the caves probably were excavated by lava flowing below the surface. After the lava disappeared, parts of the empty tubes they left behind caved in, providing the openings. The side chambers could be good places to set up lunar habitats. Most of the caves on Mars probably formed the same way. But a recent study found eight caves that might have been carved by water. The caves were seen in a region that’s marked by deep channels that carried water in the distant past. The surface water dried up long ago. But the caves could lead to buried pools of ice. If life ever evolved on Mars, it might have survived in those damp locations. So the caves could be a good place to check for life on the Red Planet. The Moon and Mars line up with the star Aldebaran in tomorrow’s dawn sky. Mars looks like a bright star to the lower right of the Moon. Aldebaran is an even brighter star, about the same distance to the lower right of Mars. Script by Damond Benningfield

Two stars that sound a bit scary peek above the southern horizon on summer nights. Together, they form the “stinger” – the end of the curving body of the scorpion. The stars are Lambda and Upsilon Scorpii. Lambda is the brighter of the two. It’s also the more complicated – it consists of three stars. The system’s details are a bit uncertain. That’s largely because its distance is uncertain. Estimates range from about 365 light-years to almost twice that range. Without a good measurement of the distance, it’s tough to figure out how big and heavy the stars really are. We do know that the system consists of a tight binary – two stars that orbit each other once every six days – plus a third star that orbits the others every three years. One of the stars in the binary is much bigger and brighter than the Sun, and 10 to 14 times the Sun’s mass. That means the star will end its life with a colossal explosion. Its close companion is maybe twice the mass of the Sun. But it’s not yet fully formed. The distant companion is another big guy – roughly 8 to 10 times the mass of the Sun. If it’s at the high end of that range, then it, too, will explode as a supernova. If not, its fate is less certain. It could become a supernova, but it also might expire in a more gentle process – a fate similar to the Sun’s. More about the scorpion tomorrow. Script by Damond Benningfield

A star system on the far side of the galaxy keeps blowing up. Since 1863, astronomers have recorded 12 outbursts from the system – the most recent just four years ago. The flare-ups are powered by a complicated interplay between a dead star and a companion that may be dying. U Scorpii probably is more than 60,000 light-years away, far on the other side of the heart of the Milky Way Galaxy. Most of the time, the system is quite faint. But during the outbursts, it can flare 10,000 times brighter in just a few hours. It starts to fade quickly, but it takes about two months to return to its “quiet” state. The system consists of two stars in a tight orbit. One of them is a white dwarf – the dead core of a Sun-like star. The other star is headed toward the same fate. It’s at the end of the prime phase of life, so it’s starting to puff up. The white dwarf “steals” some of the gas from its surface, forming a swirling disk. Some of the gas piles up on the white dwarf. Eventually, the gas gets so hot, it sets off a nuclear blast, making the system flare up. The outburst blows away all or part of the disk. Before long, though, the process starts all over again – leading to another explosion a few years later. U Scorpii is in Scorpius, which is low in the south-southeast at nightfall. The system is above the curving line of stars that outlines the scorpion’s body and tail. Script by Damond Benningfield

About 10,000 light-years from Earth, a dead star is devouring its living companion. The process creates a disk of gas that’s heated to millions of degrees, so it shines brightly. Some of the gas is fired back into space at almost the speed of light, adding to the fireworks. The system is so powerful that it’s classified as a microquasar – a smaller version of some of the brightest objects in the universe. GRO J1655-40 consists of a black hole about six or seven times the mass of the Sun, plus a close companion star more than twice the Sun’s mass. The black hole probably began as a star about 25 times the Sun’s mass. It evolved quickly, with its core collapsing to form the black hole. Its outer layers were blasted into space. Some of that material fell on the companion. Today, the black hole is pulling some of that gas away from the companion. The same thing happens in the cores of many remote galaxies. Supermassive black holes create monster disks as they pull in gas, dust, and stars. Such a disk can shine billions of times brighter than the Sun – forming a quasar. GRO J1655-40 is a smaller version of that. The system is in Scorpius, which crawls across the south on summer evenings. The microquasar is near where the scorpion’s body curves to form its tail. Script by Damond Benningfield

It’s hard to see a pattern in most of the constellations. Their stars are too faint or too spread out, or the pattern is just too obscure. Perhaps the most prominent exception is Scorpius. It takes little imagination to see the curving body of a scorpion in its stars. The scorpion skitters low across the south on summer nights. Its brightest star is Antares. The scorpion’s body and tail curl to the lower left. The head is to the upper right. It’s marked by a line of three stars. They’re about the same brightness, and they’re fairly evenly spaced. From top to bottom, the stars are Beta, Delta, and Pi Scorpii. Delta is a bit brighter than the others. All three stars are extraordinary. Each of them actually consists of more than one star. All of the member stars are quite young – no more than a few percent the age of the Sun. And most of them are big and heavy, with some of them fated to end their lives as supernovas – titanic explosions that will outshine billions of normal stars. Delta Scorpii consists of two stars. At least one of them will become a supernova. Pi Scorpii is a triple system. It also features at least one future supernova. Beta is the busiest of the systems – at least six stars, all orbiting each other in a complex gravitational ballet. Two of those stars are likely to become supernovas – briefly highlighting the head of the scorpion. Script by Damond Benningfield

Our clocks tick off a steady 24 hours per day. But if a sundial could record the time with the same accuracy, it would show that the length of the day changes. The difference is called the equation of time. Clocks measure the length of a day averaged over a full year – the Sun’s average motion across the sky. Sundials show the Sun’s true motion. Over the course of a year, the length of a solar day – the period from one local noon to the next – varies by almost a minute. And that adds up. In early February, a solar day lasts about 14 minutes less than 24 hours. In early November, it lasts about 16 and a half minutes more than 24 hours. The change has a couple of causes. Earth’s orbit is lopsided, so our planet travels at different speeds. When we’re closest to the Sun, we move faster than average; when we’re farthest, we move slower. But the rate at which Earth spins on its axis remains the same. The difference in those two motions causes the Sun to move a little faster or slower across the sky, changing the length of a solar day. And Earth’s axis is tilted, so the poles take turns dipping toward the Sun. Today is the June solstice, so the north pole is tilting sunward. The change in the Sun’s position as a result of that tilt adds to the complexity. The solar day is exactly 24 hours long around June 13th. So now, the equation of time is almost zero – a close match between the sundial and the clock. Script by Damond Benningfield

Summer arrives here in the United States in the wee hours of tomorrow morning – the moment of the June solstice. At the solstice, the Sun stands farthest north for the entire year. For people at about 23-and-a-half degrees north latitude, our star will pass directly overhead at local noon. That line of latitude is known as the Tropic of Cancer. It was named a couple of thousand years ago. At the time, the Sun appeared against the constellation Cancer at the solstice. Today, though, the Sun’s almost directly astride the border between Taurus and Gemini. It’s on the Taurus side at the exact moment of the solstice, but it slides into Gemini a few hours later. The change in address is the result of a slow “wobble” in Earth’s axis. As it wobbles, the Sun shifts position against the background of stars. It takes our planet about 26,000 years to complete a single wobble, so that’s how long it takes the Sun to move all the way across the zodiac. So the Sun will return to Cancer in about 24,000 years. Earth’s axis also nods up and down a little over an even longer period – about 41 thousand years. That causes a shift in the latitude of the Tropic of Cancer. Right now, it’s moving southward at about 50 feet per year – changing the circle where the Sun stands overhead on the summer solstice. We’ll have more about the summer solstice tomorrow. Script by Damond Benningfield

A star seldom just flies apart – at least not when it’s in the prime of life. But some of them come close. One of the best examples is Regulus, the brightest star of Leo. It’s rotating so fast that it’s barely holding itself together. Regulus consists of four stars, but only one of them is bright enough to see with the eye alone. It’s known as Regulus A. It’s more than four times wider and heavier than the Sun. And it spins much faster – about 200 miles per second at the equator – almost 200 times faster than the Sun. According to studies, that’s 96 and a half percent of the speed required to make Regulus fly apart. The high speed pushes gas outward, so Regulus is about 30 percent wider through the equator than the poles. The star was spun up by a now-dead companion star. That star was more massive than Regulus A, so it lived a shorter life. As it expired, it puffed up. Regulus A then pulled gas from its surface. As the gas piled up on Regulus A, it added momentum to the star’s rotation – like pushing harder and harder on a spinning globe. The companion eventually lost all its outer layers. That left only its dead core, known as a white dwarf – a star that did fly apart, but not until the end of its life. Regulus stands close to the right or lower right of the Moon at nightfall. They stay close together as they drop down the western sky. They set around midnight. Script by Damond Benningfield

Allan Sandage once said that when he became a graduate student at Caltech, in the late 1940s, he was a “hick who fell off the turnip truck.” He fell at the feet of Edwin Hubble, the most famous astronomer of the time. Hubble was ill, so Sandage gathered data for him at the world’s largest telescope. When Hubble died, a few years later, Sandage took over much of his work. And like Hubble, he expanded the size and age of the universe, and shaped much of the debate over its fate. Sandage was born 100 years ago today, in Iowa City. He got interested in astronomy while looking through the telescope of a boyhood friend. Over the decades, he contributed to many areas of astronomy. As an example, he pioneered studies of globular clusters – large clumps of ancient stars. That work led to a better understanding of the age of the universe. Many of the stars in globulars appeared to be older than the universe – an impossibility. Sandage used that and other lines of evidence to greatly increase the known age of the universe. One line of evidence was the rate at which the universe is expanding – a number known as the Hubble constant. Hubble himself had come up with a number that was much too big, implying a much younger age. Sandage calculated a rate that was close to modern numbers. Sandage wasn’t always right. But his work shaped the field of cosmology for decades – and still has an impact today. Script by Damond Benningfield

As the Moon orbits Earth, its gravitational pull creates the ocean tides. As the “bulge” in the water laps against the continents, it creates drag that slows our planet’s rotation. That increases the length of a day by about 2.4 milliseconds per century. That doesn’t sound like much, but over the eons it adds up. That rate can be affected by big changes in Earth itself, including powerful earthquakes, volcanic eruptions, tropical storms, and more. And over the past few decades, it’s become clear that one of those factors is climate change. As Earth gets warmer, glaciers and polar ice sheets melt, raising sea level. The extra water increases the power of the tides, slowing Earth’s rotation. According to a recent study, that’s extending the day by 1.33 milliseconds per century – the highest rate of change over the past 3.6 million years. And the rate could get even bigger by the end of the century. In fact, climate change could add more to the day than the effects of the Moon itself. As Earth slows down, the Moon moves farther away. Right now, it’s receding at about an inch and a half per year. But climate change could speed things up – pushing the Moon away. The crescent Moon is low in the west at sunset. And it has a bright companion: Venus, the brilliant “evening star.” They drop from sight a couple of hours later. Tomorrow: measuring the age of the universe. Script by Damond Benningfield

The crescent Moon charges through a rapidly disappearing group of bright stars and planets early this evening. Most of the group will be gone from view by the end of the month. As twilight begins to fade, the planet Mercury is close below the Moon. Brighter Jupiter is the same distance to the left or upper left of the Moon. Pollux and Castor, the twins of Gemini, are to the upper right of the Moon. And the brightest member of the group is farther to the upper left of the Moon: Venus, the brilliant “evening star.” Except for Venus, all the members of the group are dropping toward the Sun as seen from Earth. For Pollux and Castor, it’s because all true stars rise and set four minutes earlier each day. So every star disappears in the evening twilight at the same time every year. For Jupiter and Mercury, the descent is due in part to the same thing – the daily shift of the starry background. But it’s also influenced by the relative motions of Earth and the planets themselves. Mercury is beginning a rapid dive toward the Sun, and will cross between Earth and Sun in a few weeks. Jupiter, on the other hand, is headed toward a passage behind the Sun as seen from Earth. But Venus is actually moving farther from the Sun. It won’t reach its peak separation for two months, so it’ll remain in good view in the western evening sky into October. We’ll have more about the Moon and Venus tomorrow. Script by Damond Benningfield

Like a cosmic butterfly, a cluster of young stars is just emerging from its cocoon – a cloud of gas and dust. The cocoon `spans about 45 light-years. But some of the beautiful butterfly is already in view. Parts of the gas cloud are lit up by the brightest of the infant stars taking shape there. That creates a glowing patch of red and blue. The whole complex is known as the Cocoon Nebula. It’s about 4,000 light-years away, in Cygnus. Hundreds of stars are being born inside it. The most impressive of those stars is about 14 times as massive as the Sun, and tens of thousands of times brighter. It’s especially bright in the ultraviolet – wavelengths that are invisible to the human eye. The U-V zaps atoms of hydrogen in the nebula, splitting them apart. When the atoms re-combine, they emit red light – the main color of the nebula. The hot star also illuminates dust grains in the nebula. It doesn’t set them aglow; instead, the light simply reflects off the grains. That colors the blue parts of the nebula. Less-massive stars – stars like the Sun or even smaller – are still coming together. They won’t shine as fully formed stars for millions of years. The Cocoon Nebula is low in the northeast at nightfall. It’s to the lower left of the bright star Deneb, which marks the tail of the swan. The nebula is too faint to see with the eye alone. Script by Damond Benningfield

The Sun’s closest planet is making a pretty good appearance in the early evening. As seen from Earth, it’s just about as far from the Sun as it ever gets. It looks like a bright star low in the west-northwest beginning shortly after sunset. Mercury is getting ready to cross between Earth and the Sun – a point known as inferior conjunction. In the meantime, it’ll drop closer and closer to the Sun as viewed from Earth. It’ll vanish in the twilight in a couple of weeks. Mercury’s orbit is carrying the planet closer to Earth. Tonight, it’s about 78 million miles away. At conjunction, it’ll close to just 53 million miles. On average, Mercury returns to conjunction every 116 days. But the gap varies by more than 10 days in either direction. That’s because Mercury’s orbit is more lopsided than that of any other planet. When Mercury is closer to the Sun it moves faster; when it’s farther it moves more slowly. So the gap between conjunctions varies depending on where Mercury is in its orbit when it passes Earth. For the next few nights, look for Mercury as evening twilight fades. Although the planet is bright, it’s so low that you need a clear horizon to spot it. It lines up to the lower right of the much brighter planets Venus and Jupiter. And the crescent Moon will join the lineup on Tuesday, helping point the way to the little planet. Script by Damond Benningfield

A relic from the early universe is racing through Libra. It’s moving across the constellation at 800,000 miles per hour. That’s far faster than most of the stars around us. So it’ll move out of Libra in the blink of a cosmic eye. The star is HD 140283. But it also has a nickname – the Methuselah Star. That’s because it’s probably about 13 billion to 14 billion years old. Since the universe itself is only 13.8 billion years old, that makes the star one of the oldest anywhere. Astronomers have pieced together several bits of evidence to arrive at that age. The key bit is the star’s composition. It has very low levels of elements that are heavier than hydrogen and helium, the simplest elements. Heavier elements were created in the hearts of stars, then spewed into space when the stars died. Some of these elements then were incorporated into later generations of stars. HD 140283 has less than half a percent as much iron as the Sun, with slightly higher levels of oxygen and a few other elements. Those abundances tell astronomers the star must have been born when the universe was brand new. As night falls, the star is to the lower left of Zubeneschamali, Libra’s leading light. It’s too faint to see with the eye alone, but it is visible through binoculars. Script by Damond Benningfield

Every star in the night sky is moving – orbiting the center of the galaxy. Some are moving toward us, while others are moving away. We can’t see that motion because the stars are so remote. But we can measure it with special instruments – one of the most important techniques in astronomy. The instruments break the light of a star or other object into its individual wavelengths or colors. Each chemical element imprints its own “barcode” in that array of wavelengths. A star’s motion toward or away from us causes the barcodes to shift position. If it’s moving away from us, the shift is toward longer, redder wavelengths: a redshift. And if it’s moving toward us, the shift is toward shorter, bluer wavelengths: a blueshift. The size of the shift reveals the speed. The technique also can reveal how fast a star is spinning; the side that’s rotating toward us is blueshifted, while the opposite side is redshifted. And it can reveal orbiting companions; their gravity pushes and pulls the star, slightly changing its motion. Two bright stars with well-measured shifts are in view as the sky darkens this evening. Regulus is in the west, well to the upper left of the brilliant planets Venus and Jupiter. Its light is redshifted; it’s moving away from us at about 9300 miles per hour. Antares, quite low in the southeast, is sliding toward us at about 8600 miles per hour – giving its light a definite blueshift. Script by Damond Benningfield

For skywatchers in the United States, a grouping in the western evening sky right now is a case of the haves and the have-mores. The group is visible across the entire country. But the view gets better as you move farther south. The group features the planets Venus, Jupiter, and Mercury, and the stars Pollux and Castor – the “twins” of Gemini. Venus is the brightest member, with the twins to its right, and Jupiter and Mercury to its lower right. All five members of the group are near the ecliptic – the Sun’s path across the sky. And the angle of the ecliptic varies by latitude. As seen from the equator, the ecliptic stands almost straight up from the horizon at sunset. The Sun drops straight down below the horizon, so the sky darkens quickly. At the same time, Venus and the others stand fairly high above the horizon. They’re still well up as twilight fades. As you go farther north, the ecliptic tilts toward the south. The farther north you are, the greater that angle. So when the Sun sets, it doesn’t drop straight down – it also slides across the horizon. As a result, the sky remains bright for much longer than it does at the equator. Venus and the others are lower in the sky at sunset, so they’re more likely to be blocked by trees or mountains. And they’re immersed in the twilight longer. That leaves less time to enjoy this beautiful group of planets and stars in the evening sky. Script by Damond Benningfield

A quadruple star system in Cygnus takes the concept of a close-knit family to extremes. It consists of three big, heavy stars packed into a region smaller than the orbit of Mercury, the Sun’s closest planet. A fourth star is looking on from a wider separation – about the distance between the Sun and Jupiter, the fifth planet. The system was discovered by a planet-hunting space telescope. Over several years, it revealed two of the stars, then three, and now, four. Astronomers say the stars probably formed together, from the same cloud of gas and dust. That means the four stars are siblings. All three of the central stars are bigger, brighter, and hotter than the Sun. Two of them form a binary – they orbit each other once every three days. The more massive of those stars is already nearing the end of its life. It’s beginning to puff up. It should get so big that it will engulf its close companion. That will begin a complicated process in which all three stars should merge. Within about 300 million years, all that will be left of them is a single, heavy “corpse” known as a white dwarf. The fourth star will remain on its own. It’s about the same size and mass as the Sun. It’ll continue to shine for billions of years. Then it, too, will expire, forming another white dwarf. So this brilliant quartet will be reduced to a faint duo – two dead stars cooling and fading across the eons. Script by Damond Benningfield

Saturn has more moons than any other planet in the solar system – 274 as of this spring. All of the bigger ones are interesting worlds in their own right. Some of them are balls of ice mixed with rock. And they offer some especially eye-catching features. Mimas has a huge impact crater that makes it look like a Star Wars death star. It’s a third as wide as Mimas itself, with walls three miles high and a floor 10 miles deep. It was created by an impact that almost ripped the moon apart. Shockwaves raced all the way around Mimas, creating a jumbled landscape on the opposite side. Iapetus has a couple of giant craters. But it stands out for two other reasons. One is its coloring. One hemisphere is covered with ice, so it’s as white as snow. The other is covered with dust that’s as dark as charcoal. The other thing that makes it stand out is its shape – it resembles a walnut. A mountain range circles its equator. It’s a dozen miles wide, and averages about nine miles high. A region of Dione is marked by cliffs that form bright slashes. The cliffs are up to a thousand feet high, and they stretch across hundreds of miles. They probably formed as Dione shrank, wrinkling its crust – sculpting an intriguing feature on one of Saturn’s moons. Saturn is near our moon at dawn tomorrow. It looks like a bright star to the lower right of the Moon. But you need a telescope to see any of the giant planet’s ice-ball moons. Script by Damond Benningfield

If you look toward the west the next couple of evenings and feel like you’re having double vision – well, you are. But it’s nothing to worry about. It’s a conjunction between the two brightest points of light in the night sky – the planets Venus and Jupiter. They’re separated by less than two degrees – the width of your finger held at arm’s length. Venus is the brighter point – the brilliant “evening star.” Jupiter is only about one-seventh as bright, but it still outshines all the other planets and stars. Jupiter is the largest and heaviest planet in the solar system. It’s a ball of gas with a dense, oozy center. Its atmosphere is topped by bands of clouds painted tan, yellow, red, and ivory. The clouds reflect most of the sunlight that strikes them, making the planet bright. Venus is only the sixth-largest and -heaviest planet – right behind Earth. It’s also covered by clouds. But they don’t form colorful stripes. To the eye alone, in fact, they look featureless – a smooth blanket of white. But they’re more reflective than Jupiter’s clouds. Venus is also much closer to both Earth and the Sun than Jupiter is. That combination makes it the brightest pinpoint in the night sky. Venus and Jupiter will be closest together tonight and tomorrow night. Then Venus will pull away, increasing the gap by about one degree per night – slowly ending the “double vision” in the evening sky. Script by Damond Benningfield

Any residents of a galaxy in the constellation Serpens have a big problem: They’re being blasted by a death ray from a black hole. The galaxy is a companion to a bigger galaxy, known as 3C321. They’re more than a billion light-years away. A supermassive black hole inhabits the heart of the larger galaxy. It’s surrounded by a giant disk of gas that’s heated to millions of degrees. Powerful magnetic fields funnel charged particles from the disk into jets. They squirt away from the poles of the black hole at almost the speed of light. One of those jets is firing toward the companion galaxy, which is just 20,000 light-years away. Observations by telescopes on the ground and in space show that the jet is hitting the edge of the companion, creating a hotspot. The encounter deflects the beam off its original course, but the beam continues for hundreds of thousands of light-years. The particles and radiation in the beam could destroy the ozone layer of any planet the beam hits. That would leave the planet exposed to radiation from the beam itself, and from other cosmic sources. So anything living on the planet would be in danger. And the situation is getting even worse. The smaller galaxy appears to be just entering the black-hole jet. Over time, more of the galaxy will pass through the jet – possibly exposing even more planets to this “death ray” from another galaxy. Script by Damond Benningfield

The sky is divided into 88 official constellations. In fact, though, it’s more like 88 and a half. That’s because the constellation Serpens consists of two disconnected parts – a head and a tail. They wrap “behind” the body of Ophiuchus the serpent bearer. Serpens is in full view in the east and southeast by a couple of hours after sunset. The half that represents the head is highest, above Ophiuchus, with the tail below the serpent bearer. The front of the snake, Serpens Caput, is the more prominent half. It has several stars that are fairly easy to see. The brightest is Alpha Serpentis, also known as Unukalhai – “the serpent’s neck.” It’s a red giant – an old, bloated star that’s much bigger and brighter than the Sun. Its surface is much cooler than the Sun’s, so the star looks yellow-orange. The back half of the snake, Serpens Cauda, is tougher to spot. Its brightest star, Eta Serpentis, is the second-brightest star in the whole constellation. It’s about half as bright as Alpha. But the two stars are quite similar. Eta is also a giant – a puffed-up star that’s nearing the end of its life. It’s a little farther along than Alpha, so it’s a little bigger and brighter. It looks fainter because it’s farther away. The two stars will end their lives in the same way. Each will cast its outer layers into space, leaving behind a hot but tiny corpse known as a white dwarf. More about Serpens tomorrow. Script by Damond Benningfield

Venus and Jupiter are staging one of the top skywatching events of the year – an especially close encounter of the two brightest points of light in the night sky. It plays out in the west over the next few evenings. Venus is the beautiful “evening star” – the brightest object in the night sky after the Moon. Jupiter is the next-brightest. Even so, right now it’s only about one-seventh as bright as Venus, so it’s easy to tell them apart. The two planets can pass especially close because both of them stay near the ecliptic – the Sun’s path across the sky. They pass by each other every year or so. But both worlds wander a little bit to either side of the ecliptic, so they usually just miss each other. And even when they are close, they’re sometimes so near the Sun that we can’t see them. At times, though, Venus can pass in front of Jupiter, blocking it from view That last happened in 1818. It’ll happen again in 2065. But that’s one of those times when they’ll be too close to the Sun to see. Tonight, Jupiter is close to the upper left of Venus. But over the coming evenings, Venus will overtake it. They’ll stand side by side on Sunday, and be especially close on Monday and Tuesday – separated by about the width of your finger held at arm’s length. They don’t drop from view until about 10:30 or 11, so there’s plenty of time to watch this impressive planetary encounter. Script by Damond Benningfield

The night sky can sometimes look like a tie-dyed T-shirt flapping on a clothesline. Ribbons and swirls of bright color ripple through the sky. They can change appearance in seconds – blown by the solar wind. The colorful display is an aurora – the northern and southern lights. An aurora flares to life as charged particles from the Sun run into Earth at high speed. Earth’s magnetic field funnels the particles toward the magnetic poles. When particles hit atoms and molecules high above the surface, they knock atoms out of their usual configuration. When they return to normal, the atoms emit light. The color of an aurora depends on what the charged particles hit, and where they hit it. Most auroras are green. They switch on when particles hit oxygen molecules at altitudes of about 60 to 200 miles. Red auroras are fed by oxygen that’s even higher. The lower fringes of a display can appear pink or dark red – the result of collisions with nitrogen at lower altitudes. Collisions with hydrogen and oxygen create blue and purple auroras. But they’re not very common, and they’re hard for the eye to take in. They’re easier to see in photographs. Most of the time, the northern lights stay close to the magnetic pole. When the Sun spews out more particles, though, they can spread outward, shining in regions where they’re seldom seen. And the colors can get more intense – dramatically “tie-dying” the night sky. Script by Damond Benningfield

The goddess of the dawn has given millions of Americans a rare treat the past couple of years: brilliant displays of the northern lights in regions where they’re seldom seen. Today, we know that these colorful curtains of light are powered by storms on the Sun. Bigger storms expand the viewing area. But in centuries past, cultures around the globe created their own explanations. In Scandinavia, for example, the northern lights might have represented Bifrost, the “rainbow bridge” that connected Earth to Asgard, the home of the gods. In some of the islands of Scotland, the lights represented a pair of chieftains fighting for the hand of a “merry dancer.” In southern England, they were considered omens of misfortune. Some saw the lights as clashing swords; red lights were streamers of blood. During an intense outburst in March 1716, at the end of a civil war, people ran into the streets in their nightclothes, and some thought it was judgment day. One writer said that some “read in its glaring visage, the fate of nations and the fall of kingdoms.” The name for the northern lights – the aurora borealis – was bestowed in 1619 by Italian astronomer Galileo Galilei. Aurora was the Roman goddess of the dawn. Boreas was the Greek god of storms and the north wind – one of the namesakes of the always beautiful, sometimes frightening northern lights. More about the aurora tomorrow. Script by Damond Benningfield

Sixty years ago today, NASA was making its first attempt to land on the Moon. Surveyor 1 had been launched three days earlier. The robotic lander touched down in a crater in the Ocean of Storms – a giant volcanic plain. It was a precursor to the Apollo missions, which would land astronauts on the Moon. Surveyor wasn’t the first probe to land on the Moon – a Soviet mission beat it by a few months. But Surveyor was more sophisticated. It carried a television camera to beam back images of its surroundings. Surveyor transmitted its first pictures just minutes after landing. And during its first lunar “day” – almost 14 Earth days – it snapped more than 10 thousand images. They showed a surface coated with small rocks, and pockmarked by small craters. The rim of the crater Surveyor landed in was visible in the distance. Pictures of its landing pads revealed important details about the texture of the lunar surface, as this NASA documentary pointed out: ANNOUNCER: The lunar surface texture not thick layers of loose dust into which spacecraft or men could sink. In the area of the Ocean of Storms, man can land and walk on the lunar surface. Surveyor 1 survived the frigid lunar night, taking hundreds more pictures the next day. Scientists even raised it the following January – seven months after its historic landing on the Moon. Script by Damond Benningfield

The twins of Gemini have a front-row seat for a planetary waltz this month. Venus, Jupiter, and Mercury are close to the twins now, and will bunch up even closer as the month progresses. The “twins” are the stars Pollux and Castor. They’re about a quarter of the way up the western sky as evening twilight fades. Pollux is the brighter of the two, with Castor to its right. Jupiter looks like a brilliant star to the lower left of the twins. It’s the largest planet in the solar system. But it’s on the far side of the Sun as seen from Earth, so it’s more than 550 million miles away – about six times the distance between Earth and the Sun. Venus is even brighter – the “evening star.” It’s below the twins. Although it’s a little smaller than Earth, it shines much brighter than Jupiter mainly because it’s much closer to both Earth and the Sun. Venus and Jupiter remain in view for a good while after darkness falls. That’s not the case for Mercury. It’s well to the lower right of the others, and much lower in the sky. It’s bright, though, so with a clear horizon, there’s a good chance to spot it. Mercury will move a little higher into the sky over the next few nights, improving the view. But the real action involves Jupiter and Venus. Venus is climbing away from the Sun quickly. It will nestle especially close to Jupiter on the 8th and 9th. It’ll pull away after that – all in close view of the twins. Script by Damond Benningfield

It’s early in the long winter night at the south pole. But a few dozen scientists and others have settled in at a research base there. They monitor the weather and climate, listen to rumbles in the ice below, and watch auroras dancing in the dark skies above. And they operate observatories that study the universe beyond. One of those observatories is buried in the ice. Known as IceCube, it’s a set of thousands of light detectors. They look for evidence of neutrinos – particles that are produced in the Sun, exploding stars, and other powerful objects and events. They almost never interact with other matter. But when one does interact, by smashing into an ice molecule, it produces a quick flash of light. Studying that flicker reveals details about the neutrino, including its origin. And that tells scientists more about the body that created it. Another observatory, the South Pole Telescope, studies the “afterglow” of the Big Bang. Known as the cosmic microwave background, it’s a sort of “haze” that fills the entire universe. Tiny fluctuations in the haze reveal details about the birth of the first stars and galaxies. Water vapor in the atmosphere absorbs microwaves. But the south pole is almost two miles high, and it’s so cold that there’s almost no water vapor in the skies above it. That allows the 10-meter dish to study the background glow in great detail – under the clear, dark skies at the bottom of the world. Script by Damond Benningfield

The Moon can be like a painter’s canvas, dabbed with many colors: the silver of a frosty night, the gold of honey, the orange of a ripe cantaloupe, even the deep red of blood. But it’s almost never blue – at least not in appearance. It sometimes is blue in name, though – including tonight. That’s because it’s the second full Moon of May – a repeat appearance known as a Blue Moon. The color of the Moon – full or not – depends on several factors. When the Moon is low in the sky, as it rises or sets, its light passes through a thicker layer of air. Molecules in the atmosphere scatter blue wavelengths of light, allowing the red to shine through. As the Moon climbs higher, we see more of its true color – gray. But the Moon is so bright that it looks white or silver. During a lunar eclipse, the Moon passes through Earth’s dark shadow. But sunlight filtering through Earth’s atmosphere makes the Moon look dark orange or red. In rare cases, the Moon can actually look blue. That happens after volcanic eruptions or big forest fires. These events pump out particles that scatter red light, allowing the blue to shine through. After the eruption of Krakatoa, in 1883, the Moon appeared blue for months around the entire globe. Whatever its color, enjoy tonight’s Blue Moon. And look quite close to it throughout the night for the star Antares, the heart of the scorpion. They’ll be closest as they set. Script by Damond Benningfield

For most American skywatchers, the star Capella is just peeking into view in the morning twilight. It’s bright, but it’s quite low as the sky brightens. You need precise timing and a clear north-northeastern horizon to spot it. A star’s first appearance is called the heliacal rising – a term that means “with the Sun.” It takes place at the same time every year, as the Sun completes a full circuit through the background of stars. In many ancient cultures, the heliacal rising of certain stars was crucial. The best example is Sirius, the brightest star in the night sky. In Egypt, it first appeared just before the annual flooding of the Nile – the most important event of the year. So the star’s return marked the start of a new year. Several cultures looked for the Pleiades star cluster. Its appearance marked a time to plant crops, or to gather them, depending on a culture’s location. Capella might have been important to the Zapotec, who lived in present-day Mexico. A half-century ago, researchers proposed that a building in the city of Monte Albá‡n was intentionally aligned at a right angle to Capella’s rising point. The star first appeared there at the time the Sun passed directly overhead at noon – a key date in the calendar. But later work disputed that finding. Capella isn’t nearly as important in modern times. But it reminds us that the stars once held great power over much of everyday life. Script by Damond Benningfield

Thousands of New Yorkers and visitors will crowd the major east-west streets of Manhattan the next couple of afternoons – all to watch the setting Sun. Weather permitting, the Sun will be perfectly framed by the island’s urban canyons as it descends over the Hudson River. The event is known as Manhattanhenge. It’s named for Stonehenge, the ancient monument in England. Its stones appear to have been aligned with key sunrise and sunset points, and other events. Manhattan produces its own alignments. The island is laid out in a perfect grid, and there are no obstructions along the horizon to block the Sun. The special sunset alignment occurs twice per year, about three weeks before and after the summer solstice, in June. Today, the Sun will be half above and half below the horizon at the peak viewing time. Tomorrow, the full solar disk will stand directly atop the horizon. That sequence is reversed on the nights of July 12th and 13th. Manhattanhenge has become a popular tourist attraction. The streets are clogged by a half hour before sunset. And some venues hold special events to celebrate the view. New York isn’t the only city where you can see the Sun setting between the buildings. But few offer the same alignment of streets and the open horizon provided by Manhattan. Script by Damond Benningfield

The star Vega is a bit of a puzzler. Over the years, astronomers reported evidence of several planets orbiting the bright star. But none of the planets has been confirmed. And observations by two space telescopes revealed nothing. But they left open the possibility of planets. Vega is low in the east-northeast at nightfall, and soars high overhead later on. It’s about 25 light-years away. It’s a bit bigger, brighter, and heavier than the Sun. And it’s younger – just 10 percent the Sun’s age. A disk of dust encircles Vega. It’s tens of billions of miles wide. Hubble Space Telescope recently found a “halo” of tiny dust grains that extends tens of billions of miles beyond the disk. Hubble and James Webb Space Telescope took a good look at the system. They showed that the disk is quite smooth. It’s probably renewed by comets and asteroids. They shed material as they orbit the star, and even more when they slam together. The smoothness of the disk means there are no giant planets orbiting within it. If there were, they would clear out wide gaps. There is one gap. But it’s not completely open. So a planet several times the mass of Earth could orbit in that zone, partially clearing it out. And there could be smaller planets elsewhere in the system – especially close to Vega. But so far, there are no confirmed planets – leaving Vega to travel through space alone. Script by Damond Benningfield

On September 1st of 1859, Richard Carrington was studying the Sun, as he did every day. The British astronomer used a small telescope to project an image of the Sun on a screen. That allowed him to map the dark features known as sunspots. But on this day, Carrington saw something he’d never seen before. Bright features mingled with the sunspots. They were the first solar flares ever recorded – and still the most powerful. So the outburst is called the Carrington Event in his honor. Carrington also linked the flares to brilliant auroras seen across the globe the following day – the first observations of space weather. Carrington was born 200 years ago today, in London. He originally studied theology, but became hooked on astronomy. He joined an observatory, but left after a couple of years. He built his own observatory, in Surrey. Carrington watched the skies both day and night. He compiled star catalogs. And he made the most impressive studies of the Sun to that time, revealing some crucial details about the Sun. For one thing, it rotates faster near its poles than at the equator. For another, during the 11-year sunspot cycle, the spots move from middle latitudes to near the equator. Carrington eventually had to give up his research. When his father died, he had to take over the family brewery. His health failed as well. He died in 1875 – a pioneer at studying the Sun. Script by Damond Benningfield

Lightning may flash through the skies of Mars. But don’t expect to see big, jagged streaks like those produced by storms on Earth. Instead, they may be tiny sparks – like fireflies twinkling through a summer evening. On Earth, lightning is generated by the motions of bits of ice inside clouds. As the particles move past each other, they build up an electric charge. They dis-charge as lightning. The clouds on Mars are high and thin, so there’s no way for them to make big lightning bolts. But the dust grains that swirl through the Martian atmosphere might generate their own discharges. And two recent studies found evidence of them. In the first, researchers combed through recordings made by a microphone on the Perseverance rover. They found 55 instances of small “crackling” sounds near the rover. Almost all of them happened during dust storms, or when small dust devils passed the rover. The scientists decided the most likely explanation for the crackles was tiny discharges – “lightning” bolts about a centimeter long. In the second study, a team looked at observations made by the MAVEN orbiter. The scientists looked for radio waves produced by lightning, which are different from other types of radio from the planet. They found a single example – a possible flicker in Martian skies. Even if lightning is small and rare, it could interfere with future Mars landers – perhaps endangering instruments and people on the Red Planet. Script by Damond Benningfield

Stargazers on Mars might face one of the same challenges that often hampers a night under the stars here on Earth: clouds. A recent study found that clouds on the Red Planet tend to be thicker at night than during the day. They’re thickest in early morning and evening, especially when Mars is coldest. A fleet of orbiters and landers has been scanning the planet for decades. The probes have told us quite a bit about the Martian climate. The cloud study came from a craft that’s been in orbit since 2021. It watched the clouds both day and night. It amassed the most complete view of the nighttime sky to date. Another study looked at Martian winds. Researchers used AI to sift through more than two decades of images collected by two orbiters. The program identified more than a thousand dust devils – twisting columns of air that sweep dust high into the sky, such as this one recorded by the Perseverance rover. [dust devil sounds] Tracking the motions of the little devils allowed scientists to plot the speed and direction of the winds across the whole planet. The study revealed peak wind speeds of almost a hundred miles per hour – far faster than anything ever recorded by instruments on the surface. These studies and others are helping scientists better understand how the Martian climate works – day and night, in every season. More about Martian climate tomorrow. Script by Damond Benningfield

Time is tricky. There’s no “universal” clock ticking along at a constant rate. Instead, every clock in the universe ticks at its own rate, influenced by its motion and by the gravity of the matter around it. Those influences are built into the clocks of GPS satellites; without them, the system would fail within days. Scientists recently calculated how clocks would tick on Mars – an average of 477 millionths of a second faster per day than clocks on Earth. But as Mars orbits the Sun, that rate varies by up to 226 millionths of a second. The scientists used Albert Einstein’s theories of gravity and motion. Stronger gravity and faster motion both make a clock move more slowly as seen by an outside observer. The surface gravity of Mars is only about a third as strong as Earth’s. And because the planet is farther from the Sun, it orbits the Sun more slowly. But Mars’s orbit is more lopsided than Earth’s, so its orbital speed varies more dramatically. The changing distance also alters the gravitational influence of the Sun, as well as that of Earth and the Moon. The researchers incorporated all of these variables – and many others – to figure out the ticking of Martian clocks. Mars is working its way into the morning sky. It’s quite low in the east during dawn twilight. But the planet will climb a little higher day by day, and will be in good view this summer. More about Mars tomorrow. Script by Damond Benningfield

The Moon creeps up on the heart of Leo tonight, the star Regulus. Regulus is close to the upper left of the Moon at nightfall. The Moon will move closer before they set, around 2 a.m. They’ll be closest together as seen from the West Coast. The star we see as Regulus is called Regulus A. It’s several times bigger and heavier than the Sun, and much brighter. A tiny companion star is so close that it’s impossible to see through the glare. That duo appears to have two more companions, Regulus B and C. They form their own pair, orbiting each other once every 600 years or so. Regulus B is about 80 percent the size and mass of the Sun, and one-third as bright. Regulus C is a third of the Sun’s mass and size, and just two percent as bright. Regulus B and C are 79 light-years from Earth – the same distance as Regulus A. And they’re moving through space in the same speed and direction as the brighter star. That suggests that they’re bound to Regulus A. But they’re a long way from it – several thousand times the distance between Earth and the Sun. So astronomers haven’t watched the system nearly long enough to calculate a mutual orbit for the two pairs of stars. Estimates say it would take more than a hundred-thousand years for them to complete one circuit. So it’s possible that they’re not really bound at all – just a chance alignment at the bright heart of the lion. Script by Damond Benningfield

A space telescope is scheduled for a rescue. If the plan works, a small spacecraft will boost it to a higher orbit. That would allow the telescope to keep watching the skies for years. Neil Gehrels Swift Observatory was launched in late 2004. It watches the universe at a wide range of wavelengths, from visible light to gamma rays – the most powerful form of energy. Its original mission was to study gamma-ray bursts – the explosive deaths of massive stars. They’re among the most violent events in the universe, and among the “swiftest” – they fade in as little as a few seconds. So the telescope has to pivot swiftly when a new burst occurs – hence its name. Swift’s original altitude was 375 miles. But the Sun has been especially active in recent years. It’s heated Earth’s atmosphere, causing it to expand. That’s dragged the telescope to less than 250 miles. There’s a good chance it could fall from orbit by the end of the year. The rescue mission is scheduled for launch within a few weeks. Swift wasn’t designed to be serviced in orbit, so it’ll take some delicate maneuvering to not harm its delicate equipment. The rescue ship will spend a couple of weeks flying around the observatory, giving controllers time to plot the capture. Once latched on, the craft will boost the telescope back to its original altitude – allowing it to keep watching some of the most powerful events in the universe. Script by Damond Benningfield

The Moon lines up with the twins of Gemini this evening – the stars Pollux and Castor. Pollux is the brighter twin, and is closer to the Moon. The brilliant planet Jupiter is to the lower right of the Moon. Gemini has been around for thousands of years. Its roots trace back to ancient Babylon, as do those of many other constellations. All of them were recorded in one of the most important works of astronomy in the ancient world. Known as the Almagest, it was written by Claudius Ptolemy around the year 150. Ptolemy studied many fields, including astronomy, astrology, geology, and music theory. The Almagest is perhaps his most famous work. In it, he recorded the positions of a thousand stars, and included details on the motions of the Sun, Moon, and planets. He also discussed everything from eclipses to the length of the year. The book listed 48 constellations that were visible from northern skies – Gemini among them. The constellations weren’t given any borders – just the regions of the sky in which they appeared. And some barren regions weren’t part of any constellation. Over the centuries, astronomers shifted things around some. And they created constellations for southern skies as well. Finally, in 1930, they created an “official” list of 88 constellations. Each one was given precise borders. That gave every star a home – its own “address” in the universe. Script by Damond Benningfield

Hurricane season is whirling to life in the northern hemisphere. The giant storms twirl across the ocean, developing deadly winds, rains, and storm surges. As they grow, they trace a familiar pattern – cloud bands spinning counter-clockwise around the central eye. That spin is a result of the Coriolis effect. It’s caused by a combination of Earth’s rotation and its shape. Because Earth is a sphere, locations on the equator move more than 24,000 miles in 24 hours. Locations off the equator move a much smaller distance in the same time. So, as a storm moves across the northern hemisphere, its southern edge moves faster than its northern edge. This causes the storm to rotate counter-clockwise. The Coriolis effect is much more pronounced on the giant worlds of the outer solar system – especially Jupiter. It’s the biggest planet, and it has the fastest rotation – one turn in less than 10 hours. That combination deflects what normally would be north-south winds into east-west winds. They can blow at hundreds of miles per hour. They separate Jupiter’s atmosphere into wide bands. Individual storms – some the size of continents or bigger – spin through the bands, or along their boundaries – monster storms spinning through alien skies. Jupiter stands to the upper left of the Moon this evening. It looks like a brilliant star. The twins of Gemini are above the Moon, and we’ll have more about them tomorrow. Script by Damond Benningfield

There’s a beautiful conjunction between the Moon and the planet Venus early this evening. Venus is the “evening star” – the brightest object in the night sky after the Moon. The Moon is a thin crescent – the Sun illuminates only a sliver of the lunar hemisphere that faces Earth. We can’t see it, but the Moon is moving farther from us – by about an inch and a half per year. It’s been moving away since it was born, when Earth was young. In fact, that shift was one of the clues that led to the leading theory of how the Moon was born. In the chaotic conditions of the early solar system, Earth was walloped by a planet about the size of Mars. That blasted debris into orbit around Earth. Much of that material quickly coalesced to form one or more moons. Today’s Moon is the only survivor. The collision caused Earth to spin much faster, so a day was much shorter than it is now. Gravitational interactions between Earth and Moon have slowed us down. But they’ve also caused the Moon to slide farther away. The process isn’t smooth – the Moon speeds up and slows down. And it won’t stay smooth in the future. Given enough time, the Earth-Moon system would reach a point when the same hemisphere of Earth would always face the Moon, and the Moon would stop moving away. But that time may never come. It could be so far in the future that the Sun will have expired – perhaps destroying Earth and its slip-sliding Moon. Script by Damond Benningfield

Many astronomical discoveries have come in stages – a series of “aha” moments where we learn more about the nature of an object. A good example is Messier 13, the Great Hercules Cluster. Under especially dark skies, it’s just visible to the unaided eye, so people have known about it forever. It looks like a faint, hazy star. But during the 1700s, the cluster was “discovered” several times. The first discovery was made by Edmond Halley. Using a small telescope, he came across it in 1714. He described it as “a little patch.” Charles Messier saw it a half-century later. He described it as “round, beautiful, and brilliant.” But, he wrote, “I am sure it doesn’t contain any star.” He made it the 13th object in his catalog. In 1779, though, William Herschel contradicted Messier. M13 “is a most beautiful cluster of stars,” he wrote. Many other discoveries have followed. They’ve told us that M13 contains hundreds of thousands of stars packed into a tight ball. And the cluster is ancient – 12 billion years old or older. Messier 13 is 25,000 light-years away. In early evening, look in the east-northeast for the Keystone of Hercules – a lopsided “square” of stars. M13 is between the two stars at the top of that pattern, a bit closer to the one on the left – a giant cluster that’s still producing amazing discoveries. Script by Damond Benningfield

Most of the stars in the Milky Way orbit the center of the galaxy in the same direction as all the other stars around them, and at about the same speed. But a few follow their own paths. An example is a star at the tip of the Guitar Nebula. The nebula is a bubble of gas with an outline that resembles a guitar. It’s in Cepheus, which is low in the north at nightfall. The king’s brightest stars form an outline that resembles a child’s drawing of a house. Don’t look for the nebula, though – it’s so faint that it wasn’t discovered until 1992. The guitar was sculpted by a pulsar – the crushed corpse of a mighty star. It spins once every two-thirds of a second, emitting a beam of energy that sweeps past Earth on each turn. The pulsar was born when the star exploded as a supernova. The explosion must have been off-center, so it gave the dead core a powerful kick. The pulsar is plowing through clouds of gas and dust at almost two million miles per hour. It leaves an expanding wake behind it, like a ship traveling across the ocean. That wake is what we see as the Guitar. But there’s more to the nebula than meets the eye. X-ray telescopes in space reveal a long, high-speed “jet.” It’s firing away from the tip of the nebula at a right angle to the nebula itself. The jet most likely is powered by the pulsar’s magnetic field, which funnels charged particles away from the pulsar – an interesting note from a celestial guitar. Script by Damond Benningfield